Zool 110 Lec: Platyhelminthes, Nemertea, and Nematoda (lec 22)

bilateral, cephalization

the three introduced phyla are the origins of _____ symmetry, and ______

cephalization

has a head

acoelomate

are platyhelminthes acoelomate, coelomate, or pseudocoelomate

Group Lophotrochozoa and Clade Platyzoa

what group and clade are platyhelminthes in

Platyhelminthes

the group lophotrochozoans all have a lophophore or a trochophore, except ______

lophophore

a horseshoe shaped feeding appendage

trochophore

a free-swimming, ciliated larva of many worms and some mollusks

Phylum Platyhelminthes (flatworms)

no clear defining features (no synapomorphies), marine, freshwater, moist terrestrial habitats, bilaterally symmetric, triploblastic, acoelomate, incomplete branched gut

Turbellaria

all classes of platyhelminthes are parasitic, except the class _____

paired anterior ganglia and longitudinal nerve cords

the nervous system of platyhelminthes are made up of _____ and _____

statocysts and ocelli

the sense organs of platyhelminthes are made up of _____ and _____

fragmentation, complex parasitic life cycles, most forms are monecious, internal fertilization

characteristics of platyhelminthes reproduction

flame cells (protonephridia)

the excretory system of platyhelminthes is made up of

Turbellaria, Trematoda, Monogenea, Cestoda

what are the four classes of phylum platyhelminthes

Class Turbellaria

paraphyletic group, free-living, 4500 species, marine, freshwater, terrestrial, triclad vs polyclad gut

triclad gut

three-branched gut

polyclad

gut with many branches

planarians

freshwater turbellarians

rhabdites, muscles

class turbellaria has a ciliated epidermis with _____, body wall _____ and muscles around the pharynx

Class Trematoda

digenetic flukes, parasitic (generally of vertebrates), structurally similar to turbellarians with modifications for parasitism such as oral suckers

Class Trematoda Life Cycle (e.g. Clonorchis sinensis)

Class Trematoda Life Cycle (e.g. Schistocoma mansoni)

Class Monogea

monogenetic flukes, parasitic (typically ecoparasites of fish gills)

Class Monogea Life Cycle

single host, egg --> larva --> adult parasite

opisthapter

large, posterior attachment organ

Class Cestoda

parasitic in gut of vertebrates, no gut, absorbs nutrients through skin, longitudinal nerve cords

Class Cestoda body plan

repeating segments (proglottids) + posterior scolex to attach to the host, each proglottid contains both male and female organs

Class Cestoda Life Cycle (e.g. Taenia saginata)

adult (human) --> shelled larva (grass) --> cysticercus juvenile (cow)

eucoelomate

is phylum Nemerteans eucoelomate or pseudocoelomate

Phylum Nemertea

ribbon worms, distinguished by long evertible proboscis, 1000 species, most marine some terrestrial, most < 20 cm long

Phylum Nemertea body plan

triploblastic, true coelomic cavity (rhynchocoel) may not be homologous with coelom of other protostomes, complete digestive tract, outer circular and inner longitudinal muscles, 4 lobed brain connected to paired longitudinal nerve trunks, excretory system with flame cells

Lineus Longissimus

longest animal in the world, 60 m long and only 5-10 mm wide

clade ecdysozoa

protostomes with a cuticle that is shed (molted) through ecdysis

nematoda

which phylum is the most numerous on earth

Phylum Nematoda (roundworms)

25,000 species known, probably another 475,000 yet to be described, marine, freshwater, and soil, only have longitudinal body wall muscles, pseudocoelomate

phylum nematoda

which phylum parasitizes nearly every type of animal on Earth, including crops, domestic animals, and humans

bacteria, yeasts, fungal hyphae, algae, rotifers, tardigrades, small annelids, or other nematodes

the free-living taxa of phylum nematoda eat _____....

Caenorhabditis elegans

important model organism (nematode) for genetic research

Phylum Nematoda Life Cycle